The cross-over filter and frequency settings are really about the speaker and has zero to do with amp make or model. The gain setting is about matching the input sensitivity to the source unit. Again, not related to the amp make or model.
For an 8" HLCD, we like to run the filter in the Hi-Pass mode and find the frequency tends to fall between 80-100 Hz. Im guessing you are running these speakers bridged, so the amp is in 2 chnl mode. If so, those above settings need to be set for both halves of the amp.